The present invention relates to linear motors, and more particularly, the invention relates to linear motors provided for polyphase, e.g. three-phase a.c. energization
Linear motors are well known in the art, and they have been used for a variety of purposes. A linear motor is usually constructed to have a stationary element or stator and a movable element or armature. Construction and designs details differ depending, for example, on the mode of operation. Such a motor may be constructed to be operated by d.c., or it may be constructed as an a.c.-asynchronous motor or as an a.c.-synchronous motor. Unlike the rotor in a regular motor, the armature of a linear motor moves along a straight path which means that electrical energy is directly converted into energy of a translatory (rather than a rotational) motion. Of course, the linear path may also be a curved one depending on the purpose of the armature movement, but the armature does not have an axis of rotation as far as the linear motion is concerned.
As far as structure is concerned, the core of the stator is provided with grooves which receive the several energizing coils. An a.c. motor may have its coils connected to a three-phase power supply system. The armature may be comprised of a rail-like element made of electrically conductive material such as copper or aluminum in an asynchronous motor. A permanent magnetic element is usually used in a synchronous motor.
As far as employment and use is concerned, linear motors have been used in transportation facilities, in conveyors generally, and for baggage handling in particular; they have also been used in mining, in dragging equipment, and in cranes; linear motors are still further used in machine tools, in plotters, as drives in slides, etc. The length of such a motor depends largely on its use, and it will be appreciated that some of the uses may require very long stators. A typical example here is a transport or conveyor system using a vehicle on which is mounted an armature cooperating with the stator disposed along the track or path of the vehicle.